Support structure for fourdrinier wire adjacent the headbox consisting of a small diameter roll supported by a larger diameter master roll

ABSTRACT

A TWIN-WIRE PAPER-WEB FORMING MACHINE USES A HEADBOX DISCHARGING STOCK BETWEEN TWO FORMING WIRES, ONE OF THE WIRES BEING SUPPORTED ADJACENT THE HEADBOX BY A RIDER BREAST ROLL. THE RIDER BREAST ROLL IS IN TURN DIRECTLY SUPPORTED BY A RELATIVELY STIFF MASTER ROLL, THE BREAST ROLL HAVING A DAIMETER SIGNIFICANTLY LESS THAN THE DIAMETER OF THE MASTER ROLL WHICH RESULT IN THE BREAST ROLL BEING FLEXIBLE WITH RESPECT TO THE MASTER ROLL. THE PROFILE OF THE MASTER ROLL IS REFLECTED IN THE SURFACE OF THE BREAST ROLL THEREBY RESULTING IN CONTROLLED DEFLECTION.

SUPPORT STRUCTURE OR FOURDRINIER WIRE ADJ TTTTTT HE A S T E R R Gomw ag FIG 2 BY QI/QZ/WQ Patent Agent United States Patent 3,578,557 SUPPORT STRUCTURE FOR FOURDRINIER WIRE ADJACENT THE HEADBOX CONSISTING OF A SMALL DIAMETER ROLL SUPPORTED BY A LARGER DIAMETER MASTER ROLL Gordon Thomas Tidbury, Beaconsfield, Quebec, Canada, assignor to Dominion Engineering Works, Limited, Lachine, Quebec, Canada Filed Dec. 9, 1968, Ser. No. 782,362 Claims priority, application Canada, Dec. 26, 1967, 8,443 Int. Cl. D21f 1/40 US. Cl. 162-301 4 Claims ABSTRACT OF THE DISCLOSURE A twin-wire paper-web forming machine uses a headbox discharging stock between two forming wires, one of the wires being supported adjacent the headbox by a rider breast roll. The rider breast roll is in turn directly supported by a relatively stiff master roll, the breast roll having a diameter significantly less than the diameter of the master roll which result in the breast roll being flexible with respect to the master roll. The profile of the master roll is reflected in the surface of the breast roll thereby resulting in controlled deflection.

This invention is directed to web forming apparatus and in particular to a breast roll system for a paper machine.

In earlier web forming machines such as that described in US. Pat. No. 2,473,269, issued June 14, 1949-Char1es S. Adams; Canadian Pat. No. 614,901, issued Feb. 21, 1961David R. Webster and Canadian Pat. No. 731,383, issued Apr. 5, l966--R. M. A. T. de Montigny et al. the use of a headbox in conjunction with a drum and one or more screens passing over the drum is shown.

In machines of the prior art difficulty is experienced in positioning the lips of the slice of the headbox in relation to the drum and forming wires or screens while maintaining the screen supporting guide rolls of sufficient diameter to provide transverse support of the screen or forming wire. The present invention provides a rider breast roll of reduced diameter in supported relation with a large diameter master roll. This makes possible the desired geometry for the slice lips of the machine while maintaining desired transverse stability of the screen relative to the forming drum.

A further advantage of the present invention is the capability of providing crown to the rider breast roll either directly or by crowning the supporting master roll, whereby the transverse profile of the wedge zone formed between the surface of the forming roll and the converting surface of the screen can be controlled.

Certain embodiments of the present invention are described, reference being bad to the accompanying drawings of which FIG. 1 comprises a transverse section of the machine at the web forming section embodying a rider breast roll of the present invention, while FIG. 2 is a section taken along line 2-2 of FIG. 1 showing the deflection of rolls 17 and 18 when roll 18 is crowned.

Referring to the drawings FIG. 1 illustrates an embodiment utilizing a pair of screens or wires 10, 11 passing over a forming roll 12 and providing a wedge zone 14 into which the headbox 16 discharges. A rider breast roll 17 supports the bottom screen 11 in relation to the forming roll 12, whereby the extent of the wedge zone 14 may be closely controlled. The rider breast roll 17 is in turn supported by the master roll 18.

Either the rider breast roll 17 or the master roll 18 may be of crowned profile, in order to permit control of the transverse dimensions of the wedge zone 14. It is con- 3,578,557 Patented May 11, 1971 templated that a master roll 18 of adjustable crown, or alternative master rolls 18 having different crowns may be readily utilized to provide additional flexibility to the arrangement, in promoting flatness of the oncoming wire in the cross machine direction, for differing values of wire tension.

An off coming doctor 20, and a second doctor 21 are ice 6 illustrated in relation to the rider breast roll 1.7 and the master roll 18, respectively.

In addition to facilitating the arrangement of the screen 11 in relation to the wedge zone 14 and the headbox 16 it will be seen that the present invention provides additional flexibility of arrangement to the system not previously obtainable in the prior art.

In addition to the aforementioned benfits, the provision of a rider roll of significantly reduced diameter relative to a self-supporting breast roll provides the unobvious advantage that more control is provided over the discharge of white Water during web formation, owing to the low inherent pumping action between the rider roll and the off coming lower surface of the wire or screen.

The diameter of breast roll 17 may be sufficiently re duced so that in addition to promoting access for the headbox slice, it is flexible in relation to the relatively stiff master roll 18, to which it may thereby conform in a substantially flexible manner. Thus the longitudinal profile of the master roll, Whether crowned or straight, is reflected in the upper surface of roll 17 which contacts and supports screen 11.

While the foregoing disclosure is made in relation to a top screen 10 and a bottom screen 11 it will be understood that the present invention is also of use in a single screen embodiment such as that shown in the afore mentioned U.S. Pat. No. 2,473,269.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a web forming machine having a headbox, at least one tensioned forming wire receiving the discharge from the headbox, the improvement comprising a breast roll rotatably mounted in forming wire supporting relation closely adjacent the headbox, to position the oncoming forming wire in relation thereto, a master roll in direct supporting relation with said breast roll to provide support thereto, the diameter of the breast roll being significantly less than the diameter of the master roll whereby deflection of said breast roll is controlled.

2. The web forming machine as claimed in claim 1 wherein one of said rolls is a crowned roll.

3. The web forming machine as claimed in claim 1, including a second forming wire supported in converging relation with said at least one forming wire to form a wedge zone, having said headbox discharging between said forming wires.

4. The web forming machine as claimed in claim 2, including a second forming wire supported in converging relation with said at least one forming wire to form a wedge zone, having said headbox discharging between said forming wires.

References Cited UNITED STATES PATENTS 3,331,734 7/1967 Rojecki 162--358 2,473,269 6/1949 Adams 162-314X 3,311,533 3/1967 De Montigny et a1. 162303X 3,492,200 1/ 1970 McKie et a1. 162-358X S. LEON BASHORE, Primary Examiner R. H. TUSHIN, Assistant Examiner US. Cl. X-R. 162203, 354 

